Save QTreeView/QStandardItemModel with DataStream to file?

SGaist

@StudentScripter from what you are writing, it seems that you want to be able to store stuff in a random order and then stream them back again from that random order.

Currently there are several formats that are in fact compressed files containing several other files. Take the various office files format for example: one archive containing several files.

That said, the simple way to do it is what I wrote: you always store and load your stuff in the same order.

The more complex way is what my fellows proposed: one file per element. That way you can stream whatever you want independently.

mpergand

@SGaist said in Save QTreeView/QStandardItemModel with DataStream to file?:

it seems that you want to be able to store stuff in a random order and then stream them back again from that random order.

In this case one can use QMap to identify data by its name without any order.
I talked about that HERE

StudentScripter

@JonB Well as i found out may your XML approach seems to be a better pratice as i found out that .docx for example is just a renamed .zip archive with xml files in it.
In this case: do you know how to create such an archive containing xml files and how to read from that archive using Qt C++? Haven't found a topic on doing this in a zip like archive.

mpergand

@StudentScripter
QuaZip
KArchive
https://forum.qt.io/topic/74306/how-to-manage-zip-file?_=1702397735451&lang=en-GB

JonB

@StudentScripter
:) Either XML (more feature-rich) or JSON (simpler) could be used for storing information. You still have to decide what to put into it and what to create when reading back out of it. They are just text files with a certain format.

Qt offers support for either. Start from https://doc.qt.io/qt-6/qtxml-module.html and the QDomDocument for a full-featured, in-memory XML structure; lower-level XMLStreamWriter/Reader classes, https://doc.qt.io/qt-6/qxmlstreamwriter.html, could be used if you want to write code to just write/read a stream without memory overhead. I suspect you would want the QDocument. Or https://doc.qt.io/qt-6/json.html is where to start from for JSON support.

I'm afraid it is still down to you to write the code to decide what to put into the file and how to restore it. But as I said earlier, you won't be able to stream QTreeView or QStandardItemModel via QDataStream because they are both derived from QObject and that cannot be serialized. So you would still have to make the same choices there as to what/how to save/restore.

The "zipping like an archive" is just an optional extra at the end. It does not materially affect anything. I suggest you get your serializing sorted out before worrying about that aspect.

StudentScripter

@JonB Thank you very much. :) XML is definitely the format i would preferre in that case.
And well maybe it's really to worry about zipping the XML files later, but still wanted to know how to create a custom named zip file.
Also again thanks for your time an patience with me. I guess it can be hard to read my posts sometimes, but well i guess thats always the case with someone just starting out.

EDIT: Also could you may explain the difference between QDomDocument and XMLStreamWriter/Reader? As said i have a GraphicsScene where i want to store data for all my GraphicsItems and a TreeView where i want to store data for all my TreeView items. Im not sure a to use preferrably. So far my code with QDataStream looks like this for the GraphicsItems:


//Write to file:
QDataStream &operator<<(QDataStream &out, const ResizablePixmapItem &mPixmap)
{
    //Greift größe und Position ab
    int SceneID = mPixmap.getSceneID();
    qreal x = mPixmap.selectorFrameBounds().x();
    qreal y = mPixmap.selectorFrameBounds().y();
    qreal width = mPixmap.selectorFrameBounds().width();
    qreal height = mPixmap.selectorFrameBounds().height();
    
    qreal posX = mPixmap.scenePos().x();
    qreal posY = mPixmap.scenePos().y();
    
    QString ControlName = mPixmap.getControlName();
    int FrameWidth = mPixmap.getFrameWidth();
    int FrameHeight = mPixmap.getFrameHeight();
    
    //QPixmap mPix = mPixmap.getPixmap();
    
    QString ImageFilePath = mPixmap.getImageFilePath();
    
    
    //Speichert die Informationen
    out << SceneID << x << y << width << height << posX << posY << ControlName << FrameWidth << FrameHeight << /*mPix <<*/ ImageFilePath;
    
    return out;
}



//Read from file:
QDataStream &operator>>(QDataStream &in, ResizablePixmapItem &mPixmap)
{
    int SceneID;
    qreal rectX;
    qreal rectY;
    qreal rectWidth;
    qreal rectHeight;
    
    qreal posX;
    qreal posY;
    
    QString ControlName;
    
    //QPixmap mPix;
    
    QString ImageFilePath;
    int FrameWidth;
    int FrameHeight;
    
    in >> SceneID >> rectX >> rectY >> rectWidth >> rectHeight >> posX >> posY >> ControlName >> FrameWidth >> FrameHeight  >> /*mPix >>*/ ImageFilePath;
    
    //SetPixmap muss immer for setSelectorFramebounds kommen, damit die Größe
    //beibehalten wird
    mPixmap.setSceneID(SceneID);
    mPixmap.setPixmap(ImageFilePath);
    mPixmap.setSelectorFrameBounds(QRectF(rectX, rectY, rectWidth, rectHeight));
    mPixmap.setPos(QPointF(posX, posY));
    
    mPixmap.setControlName(ControlName);
    mPixmap.setImageFilePath(ImageFilePath);
    mPixmap.setFrameWidth(FrameWidth);
    mPixmap.setFrameHeight(FrameHeight);
    
    return in;
}

mpergand

@StudentScripter
XML is tedious to use, json easier IMO.

StudentScripter

@mpergand Would you say json is more sufficient for my case? As said i may need to save hundreds of GraphicsItems where each Graphicsitem has 50+ different Variables. Also it must be working fine and save on mac, window, linux. (But well i think in this regard their is no big difference between XML and Json.)

SGaist

@StudentScripter said in Save QTreeView/QStandardItemModel with DataStream to file?:

@mpergand Would you say json is more sufficient for my case? As said i may need to save hundreds of GraphicsItems where each Graphicsitem has 50+ different Variables. Also it must be working fine and save on mac, window, linux. (But well i think in this regard their is no big difference between XML and Json.)

50+ different variables per items ?
How are you getting the values for them ?
As it is, it sounds like an architectural issue in the making. You are likely trying to store the same data at least twice.

mpergand

@StudentScripter
I don't know about efficiency.

In XML, you have two kind of parser:
-DOM parser where the xml file is loaded in memory.
-Stream parser where the xml file is read like a file stream (IODevice), more suitable for large files.

Reading an XML document with Qt's DOM classes is a straightforward process. Typically, the contents of a file are supplied to QDomDocument, and nodes are accessed using the functions provided by QDomNode and its subclasses.
The aim is to use the structure provided by QDomDocument by wrapping QDomNode objects in item objects similar to the TreeItem objects used in the Simple Tree Model example.

https://doc.qt.io/qt-6/examples-xml.html

JonB

@StudentScripter
Regardless of which way you serialize (binary, XML, JSON, anything).

You presumably have a QTreeView, bound to a QStandardItemModel. (I guess you have figured how to make that hierarchical.) It is usual to serialize the model but not the view. You find whatever data you have in the model and save/restore that. (And if you can correctly recreate a QStandardItemModel you may not need to worry about saving/restoring recursively.)

You would not normally have anything of the QTreeView to save, why/what would you want with it? What data/settings are in your treeview which are not in your model, which will be restored? Same goes for the "50+ variables", aren't they in your model?

StudentScripter

@JonB The 50+ Variables are stored within my QGraphicsItem Subclass for my GraphicsScene. I want to save the items for my GraphicsScene with their variables as listed above aswell as my QStandardItems for my QTreeView. And yes I subclassed QStandardItemModel, but im building no hierachy there. The hierachy is build by the user using drag and drop.

In shematic: I want to have 2 files XML or Json
-1 file for: All QGraphicsItems with their Variables like Height, Width, Name, ID

int SceneID = mPixmap.getSceneID();
    qreal x = mPixmap.selectorFrameBounds().x();
    qreal y = mPixmap.selectorFrameBounds().y();
    qreal width = mPixmap.selectorFrameBounds().width();
    qreal height = mPixmap.selectorFrameBounds().height();
    
    qreal posX = mPixmap.scenePos().x();
    qreal posY = mPixmap.scenePos().y();
    
    QString ControlName = mPixmap.getControlName();
    int FrameWidth = mPixmap.getFrameWidth();
    int FrameHeight = mPixmap.getFrameHeight();

-2n file to save: my QStandardItems/Model. The model looks like this (but i also have an custom StyledItemDelegate, but i guess i don't have to save that)
My full subclassed QStandardItemModel:

#include "ViewLayerStandartItemModel.h"
#include "ViewLayerList.h"
#include <QMimeData>
#include <QDataStream>

ViewLayerStandartItemModel::ViewLayerStandartItemModel(int rows, int columns, QObject *parent)
    : QStandardItemModel(rows, columns, parent)
{

}





Qt::ItemFlags ViewLayerStandartItemModel::flags(const QModelIndex &index) const {
    Qt::ItemFlags defaultFlags = QStandardItemModel::flags(index);

    // Überprüfen Sie, ob der Index zu einem Ihrer speziellen Delegaten gehört
    if (!data(index, CanHaveChildrenRole).toBool()) {
        return (defaultFlags & ~Qt::ItemIsDropEnabled) | Qt::ItemIsDragEnabled; // Entfernen Sie das ItemIsDropEnabled-Flag und fügen Sie das ItemIsDragEnabled-Flag hinzu
    }
    
    



    return defaultFlags | Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled; // Fügen Sie das ItemIsDragEnabled und ItemIsDropEnabled Flag hinzu
}








Qt::DropActions ViewLayerStandartItemModel::supportedDragActions() const
{
    return Qt::MoveAction;
}



Qt::DropActions ViewLayerStandartItemModel::supportedDropActions() const
{
    return Qt::MoveAction;
}

mpergand

@StudentScripter
As I said earlier, you can serialize an array or a map of json/xml text, no need for a zip file.

For the performance of json, have a test yourself, create a json with a thousand of parameters and look how it works.